I have used Arduino Uno, Mega and D1 to read the pressure sensor analogue output with no problem. These sensors have 3 wires and require power from the Arduino board. Now, I have a flowmeter that only has two wires. It is one for analogue output and one for GND (I guess). The device voltage output shows fine on this data logger which shows voltage of 0.06v and 1.43v when the flowmeter working (each voltage change means 10 Lit).

Reads an analog input on pin 0, converts it to voltage, and prints the result to the Serial Monitor. Graphical representation is available using Serial Plotter (Tools > Serial Plotter menu). Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

The two wires connect to a reed switch that closes when the impeller wheel moves a magnet close to the switch. Change the input setup to be "pinMode(A0, INPUT_PULLUP);" and you do not need an external resistor*. Wire the switch to A0 and GND. You then read the frequency of the digital input which is the flow rate. You can use this to get started: